Question 236458
Well you have a rectangle of length x + 4cm multiplied by x:

(x+4)*x = x^2+4x (this is the original area of the rectangle)

The length and width are reduced by 2cm so:

(x+2)(x-2) = x^2+4 (this is the new area of the rectangle)

So the original area of the rectangle is decreased by 24cm^2 so:

x^2-4 = x^2+4x-24

Rearrange to find x gives:

-4 = 4x-24

x = 20/4

x = 5

So dimensions of the original rectangle are 9cm by 5cm.

To double check we do 9*5 = 45 cm^2
                      7*3 = 21 cm^2
 
Difference of 24cm^2

Does this make sense?